Dessy its hard for anyone to answer that for you, you know yourself you should probably map for it to get its full gain and be safe. But maybe you could chance it.. its really up to you.
If your car is v5 then you should have yellow 440cc injectors? same as v5 sti.
If it were me, i would do exactly what Richie with white UK Saloon done, and basically set your self up with sti bits, Sti5 intercooler, vf28 and 440cc injectors, and then a walbro pump, pfr7b plugs, exhaust system and remap, Think Andy F told Richie she was up around 300bhp with the sti bits on. Richie was really impressed with how the car changed.